Banks are closely concerned with the flow of money into and out of the economy. They often co-operate with governments in efforts to stabilize economies and to prevent inflation. They are specialists in the business of providing capital, and in allocating funds on credit. Banks originated as places to which people took their valuables for safe-keeping, but today the great banks of the world have many functions in addition to acting as guardians of valuable private possessions.
We can say that the primary function of a bank today is to act as an intermediary between depositors who wish to make interest on their savings, and borrowers who wish to obtain capital. The bank is a reservoir of loanable money, with streams of money flowing in and out. For this reason, economists and financiers often talk of money being "liquid", or of the "liquidity" of money.